A reusable launch system includes one or more reusable components and is capable of launching a payload (e.g., into orbit). Some reusable launch systems include a reusable booster or first stage and a reusable spacecraft, like the Space Shuttle. In such reusable launch systems, the reusable booster launches the reusable spacecraft (e.g., the Space Shuttle Orbiter) or a reusable upper stage rocket into orbit. The reusable spacecraft (e.g., the Space Shuttle Orbiter) or the reusable upper stage rocket includes an internal payload bay and achieves orbital flight before deploying a payload from the internal payload bay. The separation between the reusable booster and the reusable spacecraft occurs at a positive angle of attack. Launching a reusable booster to orbit requires high forces and energy (roughly 30 times more energy) as compared to launching a reusable booster to sub-orbital altitudes. Additionally, operating a reusable spacecraft has increased costs as compared to systems that use a reusable booster to launch the payload (e.g., via an expendable upper stage rocket) into orbit from a sub-orbital altitude.
Other configurations use a reusable booster to launch an expendable upper stage rocket into orbit to deploy a payload. These configurations generally include multiple stage rockets with vertically stacked stages that take-off vertically and land vertically. Prior to separation of the upper stage, the booster engines are deactivated (e.g., main engine cut off (MECO)). Prior to and during separation of the upper stage rocket, the booster and the upper stages are oriented at a positive angle of attack. Reuse of the booster involves landing the booster vertically (e.g., in an upright or launch position) which is extremely complex and generally requires engine assistance, complex control systems, flip maneuvers, etc.
Alternatively, an assisted take-off reusable launch system deploys from an aircraft and uses a horizontally stacked configuration. The assisted take-off reusable launch system separates from the aircraft within the Earth's atmosphere at conditions where dynamic air pressures are relatively high (e.g., at relatively low altitudes where the Earth's atmosphere is relatively more dense). The low speeds and high dynamic pressures allows for a more controlled and reliable separation of the payload and the aircraft. For example, separation can occur with lower forces.